The present invention relates generally to the communication of real time media, such as media data formatted pursuant to RTP (real-time transmission protocol), in a radio communication system. More particularly, the present invention relates to apparatus, and an associated method, by which to facilitate handover of communications from a source radio gateway to a target radio gateway when real-time media data is communicated by discontinuous transmission and when real-time media is communicated pursuant to a multiple call connection. Operation of an embodiment of the present invention reduces the possibility that media frames might be erroneously sent to a source, rather than a target, gateway.
Advancements in communication technologies have permitted the introduction of, and popularization of, new types of, and improvements in existing, communication systems. Increasingly large amounts of data are permitted to be communicated at increasing throughput rates through the use of such new, or improved, communication systems. As a result of such improvements, new types of communications, requiring high data throughput rates, are possible. Digital communication techniques, for instance, are increasingly utilized in communication systems to efficiently communicate digital data, and the use of such techniques has facilitated the increase data throughput rates.
When digital communication techniques are used, information which is to be communicated is digitized. In one technique, the digitized information is formatted into packets, or frames, and, once formatted, the data is communicated upon a communication channel, thereby to be transmitted to a destination. Individual ones, or groups, of the packets or frames of data can be communicated at discrete intervals, and once communicated, concatenated together to recreate the informational content contained therein.
Because data formatted in this manner can be communicated at the discrete intervals, a communication channel need not be dedicated solely for the communication of data generated by one sending station to one receiving station, as conventionally required in circuit-switched communications. Instead, a single channel can be shared amongst a plurality of different sending and receiving station-pairs. Because a single channel can be utilized to effectuate communications by the plurality of pairs of communication stations, improved communication capacity is possible.
Also through the use of digital communication techniques, any of a large number of different types of data can be communicated. And, more than one type of data can be communicated in a multi-media application. Different types of data exhibit different communication requirements however. For instance, voice data must be communicated in real time. That is to say, voice data must be communicated without significant delay and must be communicated in a manner which permits its reconstruction at a receiving station in a manner which introduces minimal time distortion. Otherwise, the voice data shall appear to be noticeably distorted.
Internet telephony is exemplary of communications which can be effectuated utilizing digital communication techniques. With the popularization of the Internet and communication thereon, standardized protocols have been set forth by which to communicate information in a form amenable to its transmission by way of the Internet. An example protocol is H.323. H.323 is a widely used ITU standard which uses RTP (real-time transmission protocol).
According to the H.323 protocol, when data is to be transmitted by a sending station, logical channels upon which to transmit the data are assigned. The data channels are allocated responsive to requests made by the sending station. Separate logical channels are requested for separate types of data. For instance, a first logical channel is requested upon which to transmit voice data, and allocation of a second logical channel is requested for transmission of non-voice data. A subset of the H.323 protocol, referred to as the H.245 protocol, defines the manner in which the channels are requested. Data is thereafter transmitted upon the logical channels. In conventional manner, individual packets, or frames, include header information, such as IP, UDP, and RTP information, to identify to where the packet is to be directed and to provide a time stamp with the packet. The informational content, referred to as the payload, is appended to the header information.
The H.323 protocol was intended originally for wireline communications, such as between communication stations, connected by wireline connections including those of the Internet. But, advancements in communication technologies have also permitted the widespread usage of radio communication systems. A cellular communication system is exemplary of a wireless communication system which has achieved wide levels of popularity and usage. Telephonic communication by way of a cellular communication system mimics communication by way of a conventional, wireline, telephonic system. However, difficulties arise when packet or frame-formatted data, such as that formatted pursuant to the H.323, or other RTP, protocol is communicated by way of a cellular communication system.
In general, a handover of communications occurs from a source gateway to a target gateway when a mobile station is repositioned out of proximity with a source gateway and into proximity with a target gateway.
When a determination is made that a handover should be effectuated, a selection is made of the target gateway and thereafter, the handover is performed. Conventional handovers assume an active communication session between a mobile station and another communication station. But in H.323-based communications, the communication session might not be active at the moment of handover.
For instance, due to the discontinuous nature of packetized communications, such as pursuant to DTX transmissions, a handover of communications of a mobile station operable in the cellular communication system during a communication session might not be immediately reported to the other communication station of the communication session. In such an occurrence, the other communication station might not properly route downlink data to permit its efficient transmission to the mobile station. A similar misrouting of data might also occur if the mobile station is operable pursuant to multiple-call connection. An example multiple-call connection is a situation in which one call, or communication session, is in an active mode and one, or more, other call, or communication sessions, is in an inactive mode, such as a call placed on hold, mode.
That is to say, a communication session is susceptible to misrouting of data when DTX transmission is utilized and data frames are not being communicated by a mobile station at the moment of handover from a source to a target gateway.
A manner by which to inform a communication station of a handover of communications would facilitate improved communications by reducing problems conventionally associated with misrouting of data frames subsequent to a communication handover.
It is in light of this background information related to radio communications that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides, apparatus, and associated method, for facilitating communication handovers between radio gateways in a packet radio communication system.
In operation of an embodiment of the present invention, a default frame is generated at the target gateway responsive to indications received thereat of the handover of communications thereto. The default frame is transmitted to a communication station with which a mobile station is paired pursuant to a communication session. The default frame identifies, to the communication station, the identity of the target gateway. Thereby, the communication station is informed that the target gateway is the address through which additional data generated at the communication station is to be routed. And, as a result of such identification, the possibility that media frames might erroneously be sent to a source gateway instead of the target gateway is reduced.
In one implementation, an embodiment of the present invention is operable at a radio gateway positioned between the packet data network and a radio network. When a handover of communications is effectuated to the radio gateway, here referred to as the target gateway, from another gateway, referred to here as a source gateway, indications of the handover are provided to a RTP handler. The indications of the handover are, for instance, uplink data frames generated by the mobile station. The uplink data frames, might for instance, be formed of a normal speech frame, an SID (silent descriptor) frame, or an idle frame. The RTP handler includes a default frame generator which is also provided with the indications of the effectuation of the handover of communications. Responsive to detection of the indications of the handover, the default frame generator generates a frame for transmission to the communication station which forms the other part to the communication session. The default frame identifies the target gateway at the gateway through which data frames originated at the communication station should be routed. Thereby, the communication station is notified of the identity of the target gateway. Transmission of subsequent frames of data to an erroneous, i.e., the source, gateway can thereby be prevented.
In one implementation, the frames of data are formatted pursuant to the H.323, or other RTP, protocol. And the data frames are communicated to effectuate Internet telephony between a mobile station and a communication station. As the mobile station travels through a geographical area encompassed by one radio gateway into an area encompassed by another radio gateway, a communication handover is effectuated to permit continued communications between the mobile station and a communication station. The radio gateway from which communications are handed over are referred to as the source gateway, and the gateway to which communications are handed over is referred to as the target gateway. As soon as the target gateway receives indications that a communication handover is to be effectuated thereto, a default frame generator located at the target radio gateway generates a default frame which is transmitted to the communication station involved in the communication session. The default frame identifies the target radio gateway with its identity, thereby to inform the communication station that subsequent data frames to be communicated to the mobile station should be routed through the target radio gateway.
An embodiment of the present invention is also operable in an Internet telephony scheme in which the mobile station is capable of multiple call operation. For instance, a mobile station operable pursuant to a multi-call scenario is capable of maintaining two, or more, communication sessions concurrently. For instance, one communication session might be in an active state in which communication frames are exchanged between the mobile station and another communication session might be in an inactive state, such as a call placed in an xe2x80x9con-holdxe2x80x9d condition. When a communication handover is effectuated from a source gateway to a target gateway while the mobile station is in such concurrent communication sessions, the first communication station operable in the active communication session is notified immediately of the communication handover. But, the communication station operable in the inactive communication session is not conventionally immediately notified of the communication handover. In operation of an embodiment of the present invention, a default frame generator is operable to generate a default frame for transmission to the communication station to inform the communication station of the communication handover. Thereby, the communication station operable in the inactive communication session is also immediately notified of the handover.
In a further implementation, the target radio gateway is further operable to detect whether uplink data frames received thereat, presumptively from a mobile station, contained valid data. If a determination is made that the data is invalid, a default frame generator is again utilized to generate a default frame. The default frame is transmitted to the destination. Thereby, invalid data is not forwarded to the communication station.
In these and other aspects, therefore, apparatus, and an associated method, for a target gateway forming a portion of a radio communication system. The radio communication system is operable to permit communication of packet-formatted data between a first communication station and a second communication station. The first communication station forms a mobile station, and the communication network includes a source gateway through which communications are initially effectuated, and the target gateway through which communications are subsequently selected to be effectuated. The apparatus informs the second communication station of selection of the target gateway for effectuation of subsequent communications therethrough. A default generator is coupled to receive indications of selection of the target gateway through which to effectuate the subsequent communications. The default frame generator generates a default frame for transmission to the second communication station. The default frame identifies the target gateway, thereby to inform the second communication station of the selection of the target gateway for the effectuation therethrough of the subsequent communications.
In these and other aspects, apparatus, and an associated method, is further provided for a radio communication system operable to permit concurrent communication of packet-formatted data between a mobile station and a second communication station and between the mobile station and a third communication station. The packet-formatted data is communicated by way of a communication network having a radio part and a wireline part. The communication network includes a source gateway through which communications are initially effectuated and a target gateway through which communications are subsequently selected to be effectuated. At least one of the concurrent communication sessions is in an inactive state when the effectuation of the subsequent communication through the target gateway occurs. A timer is located at the at least one of the second and at least third communication stations in the inactive state when the effectuation of the subsequent communication occurs. The timer times periods of absence of incoming data during a communication session with the mobile station and generates a request to alter communication session parameters if a timed period of the absence of incoming data exceeds a selected time.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings which are briefly summarized below, the following detailed description of the presently-preferred embodiments of the invention, and the appended claims.